1. Technical Field of the Invention
The present invention relates to an integrated sealed secondary battery wherein a plurality of cells are arranged in a row, thereby forming a one-piece battery housing.
2. Description of Related Art
FIG. 16 shows a known integrated sealed secondary battery of this type disclosed in Laid-open Japanese Patent Publication No. 7-85847. Electricity-generating elements are accommodated respectively in cases 63 formed in rectangular tubular shape having a bottom, and the apertures of the cases 63 are sealed by covers 64, thereby constituting cells 62. A plurality of these cells 2 are arranged in a row, and the cases 63 of these cells 62 are tightly bound together with end plates 65 and restraining bands 66. Positive electrode terminals 67 and negative electrode terminals 68 of cells 62 pass through the covers 64, projecting upwardly, and these terminals 67, 68 are connected successively in series by electrical connection bars 69.
The mono-block rechargeable battery disclosed in Laid-open Japanese Patent Publication No. 6-215804 in which a battery housing and a cover made of plastics material are heat-welded is constructed as follows. Side plates having concave spaces on the inside thereof are heat-welded to the outside faces of opposite side walls of two battery housings, whereby a cooling jacket is formed between the side walls of the battery housings and the side plates. A cooling liquid inlet orifice and outlet orifice are provided at the top of the two ends of the side plates. Within the cooling liquid jacket, flow-alignment projecting strips are provided alternately from the top surface and bottom surface of the interior of the cooling jacket for forming a meandering flow passage, and, furthermore, air escape apertures of about 1 to 3 mm are formed between the top face and the tops of the flow-alignment projecting strips that extend downwards from the top face.
Laid-open Japanese Patent Publication No. 61-45571 discloses the provision of cooling passages that pass through upper and lower portions of partitions between cells in a mono-block housing, and the provision of cooling medium inlet/evacuation headers thereabove and therebelow, separate covers being provided for each cell.
However, with the integrated sealed secondary battery of Laid-open Japanese Patent Publication No. 7-85847, since the cells are tightly bound in close contact, if the ambient temperature is high or if discharge is effected with large current, heat cannot be removed sufficiently from the cells. There is therefore the problem that the temperature of the cells rises, lowering cell life.
In this regard, in the rechargeable battery of Laid-open Japanese Patent Publication No. 6-215804, temperature rise can be suppressed to some extent since both side faces of the battery housing are cooled by the cooling jacket. Also, the meandering flow passage formed within the cooling jacket enables uniform cooling of the entire surface of the side walls of the battery housing. Furthermore, since air escape apertures are formed in the corners where the top wall of the cooling jacket and the flow-alignment projecting strips are connected, the loss of cooling performance produced by stagnation of air taking place in these corners can be suppressed to some extent. Nevertheless, in the case of a secondary battery in which cells are integrated as shown in FIG. 16, the temperature rise of the cells cannot be sufficiently suppressed, because of insufficient cooling between the cells.
In order to solve the problem of the integrated sealed secondary battery of Laid-open Japanese Patent Publication No. 7-85847 referred to above, the inventors of the present application have performed various studies, in which spaces were provided between the cells so as to form cooling passages and this was combined with the cooling jacket as disclosed in Laid-open Japanese Patent Publication No. 6-215804. The results shows that the cooling medium tends to stagnate particularly in the corners of the flow-alignment projecting strips and the top wall of the cooling jacket, which was found to be the main cause of drop in cooling performance. It was further ascertained that small air escape apertures provided at the corners of the flow-alignment projecting strips had little effect of causing cooling medium to flow smoothly and air to be discharged.
In the case of the rechargeable battery of Laid-open Japanese Patent Publication No. 61-45571, while the region where the cooling passages are formed that pass through upper and lower portions of partitions between the cells in the mono-block housing is forcibly cooled, the cooling effect is still insufficient, since the entire outside surface of the cells is not forcibly cooled. There are also the problems that, since the construction of the housing is complicated, manufacturing costs are high and, since it is necessary to provide a cover for each cell, a large number of separate operational steps are required in assembly, also raising the cost.
In view of the above problems, an object of the present invention is to provide an integrated sealed secondary battery which is of an inexpensive construction and wherein the cells can be effectively cooled.
Another object of the present invention is to enhance cooling effect of each of the cells by causing cooling medium to flow efficiently in cooling medium passages provided between the cells. Yet another object of the present invention is to prevent drop in the cooling effect by preventing air stagnation in the cooling medium passages.
The present invention provides an integrated sealed secondary battery comprising: a plurality of cells arranged in a row respectively accommodating electricity-generating elements within rectangular tubular cases having a bottom, with their upper open ends being sealed; first cooling medium passages formed on both sides of the row of the cells; second cooling medium passages formed between the cases of the cells that communicate with the first cooling medium passages on both sides of the row of the cells; and means for generating pressure difference at both ends of the second cooling medium passages between the cases.
With this construction, all of the side faces of the cells, including those between the cells, can be forcibly cooled by the cooling medium passing through the cooling medium passages between the cases and the cooling medium passages on both sides. While cooling medium tends to flow out smoothly when it is made to flow through the cooling medium passages on both sides, it tends to stagnate in the cooling medium passages between the cases that are branched from the cooling medium passages on both sides. However, thanks to the provision of means for generating a pressure difference at both ends of the cooling medium passages between the cases, it can be made to flow reliably through the cooling medium passages between the cases. Consequently, all of the cells can be effectively cooled.
Means for generating a pressure difference at both ends of the cooling medium passages between the cases may be constructed in various manners as will be described in detail later. For example, the flow path cross-sectional areas of the cooling medium passages on both sides may be mutually differed. Such is a comparatively straightforward arrangement and does not involve large pressure loss, whereby pressure difference can be created such as to cause suitable flow of the cooling medium through the cooling medium passages between the cases.
The present invention also provides an integrated sealed secondary battery comprising: a plurality of cells arranged in a row respectively accommodating electricity-generating elements within rectangular tubular cases having a bottom with their upper open ends being sealed; first cooling medium passages formed on both sides of the row of the cells; second cooling medium passages formed between the cases of the cells that communicate with the first cooling medium passages on both sides of the row of the cells; projection strips provided in the first cooling medium passages such as to alternately extend downwards from a top wall and upwards from a bottom wall of the first cooling medium passages so that the first cooling medium passages meander upwards and downwards; and air escape apertures formed between the top wall of the cooling medium passages and top ends of the projection strips that extend downwards from the top wall of the cooling medium passages.
Even when air stagnates in the corners between the tops of the flow-alignment projecting strips and the top wall of the cooling medium passage, this air is moved through the air escape apertures towards the downstream side, until it is finally discharged from the cooling medium passage. Loss of cooling performance due to the occurrence of air stagnation in the meandering passage can be thus reliably prevented.
Inclined faces may be formed that are inclined towards their sides in at least portions facing the air escape apertures of the top walls of the cooling medium passages. Thereby, even if air stagnates in these corners, it can be shifted towards the middle of the meandering flow passage by the inclined faces, through the air escape apertures. Stagnant air is entrained by the strong current of cooling medium flowing through the meandering flow passage, shifting it downstream, so the lowering of cooling performance caused by stagnation of air in the meandering flow passage can be even more reliably prevented.
Alternatively, inclined faces may be formed that are inclined upwards towards the outlet from the inlet of the cooling medium passages in the top walls of the cooling medium passages. Thereby, the air passes successively through the air escape apertures along these inclined faces as far as the outlet of the cooling medium passages, where it is smoothly discharged.
The height positions of the tops of the flow-alignment strips may be made practically the same, and the aperture area of the escape apertures may be made progressively larger from the inlet end towards the outlet end of the cooling medium passages. Thereby, it becomes progressively easier for the air to flow out, as it proceeds towards downstream, making it possible for the air to be evacuated even more smoothly.
Alternatively, the air can be evacuated smoothly by forming inclined faces which are inclined upwards towards both sides from the portion opposite the air escape apertures in the top walls of the cooling medium passages.
The angle of inclination of the inclined faces with respect to the horizontal plane should preferably be 3 to 5xc2x0, and the vertical width of the air escape apertures should preferably be 3 to 5 mm, so that air stagnating in the corners between the top ends of the flow-alignment projecting strips and the top walls of the cooling medium passages can be reliably shifted towards the middle of the meandering flow passage, making it possible to reliably prevent lowering of cooling performance caused by stagnation of the air.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.